High-frequency tube structure



3 Sheets-Sheet l W. W. HANSEN HIGH-FREQUENCY TUBE STRUCTURE OM MN i .l l V 1 1 1|] n m! e1 May 9, 1950 Filed oct. 51, 1941 h NMWIHMHH. Il l lvv n* wv ...vm Ov Nv. Ov

A. R ..U-L WN May 9, 1950 w. w. HANSEN 2,506,590

HIGH-FREQUENCY TUBE STRUCTURE Filed Oct. 51, 1941 3 Sheets-Sheet 2 C I I WILLIAM W. HANSEN TTORNEY,

5 sheds-sheet 3 Filed Oct. 5l, 1941 Patented May 9, 1950 UNITED STATES PATENT OFFICE HIGH-FREQUENCY TUBE STRUCTURE William W. Hansen, Garden City, N. Y., assignor to The Sperry Corporation, a corporation of Delaware 22 Claims.

This invention relates, generally, to high frequency tube structures having attached resonant members and of the type shown in Patent No. 2,242,275, issued May 20, 1941, in the name of Russell H. Varian, and more specifically, to a high frequency tube structure of the above type having very large power output.

Stated somewhat fully, the principal object of the invention is the provision of an improved and practicable embodiment of high frequency tube structure utilizing principles disclosed in the above-identified patent, the device in the present invention employing two hollow resonators with an electron beam projecting through them, the second of said resonators being arranged in sections such that a unidirectional voltage may be applied between the sections of said resonator.

More broadly, an object of the invention is to provide high frequency tube structures, useful as high power power-ampliers, oscillators, modulators, multipliers, detectors, etc.

Another object of the invention is to provide an improved resonator structure suitable for use in the aforementioned type of tube structures and having a construction such that unidirectional or modulating voltages may be applied between the grids or active portions of said resonator.

A further object of ther present invention is to provide an improved electron tube device formed substantially as a figure of revolution.

Another object of the present invention is to provide a low pass lter construction suitable for use with such a resonator, and having characteristics such that unidirectional voltages may be applied through the llter to the resonator grids or active portions and such that ultra high frequency current does not leak out of the resonator at the point of application of the unidirectional voltage.

' A further object of the invention is to design 'a portion of such a resonator so that said portion acts as the rst element of such a filter.

A still further object of the invention is the provision of an ultra high frequency tube structure suitable for use as a power amplifier, an oscillator, or for other uses, having annular resonators, grids, and an annular filter structure, and capable of a very high power output.

Still another object of the invention is to provide a low pass filter suitable for filtering out ultra high frequencies and passing only unidirectional voltages such as are useful for beam voltages, heater voltages, control voltages, or buncher resonator acceleration voltages, or for such as are used in the aforementioned ultra high frequency tube structures.

Other objects and advantages will become apparent from the specification, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In the drawings,

Fig. 1 is a fragmentary cross-section view of a preferred form of the invention.

Fig. 2 is a longitudinal cross-section view of a low pass filter structure, useful in explanation of the operation of a portion of the structure shown in Fig. 1.

Fig. 3 is an equivalent circuit of the lter of Fig. 2.

Fig. 4 is an explanatory diagram useful in explaining the operation of the invention.

Fig. 5 is a further explanatory diagram.

Fig. 6 is a cross-section view of a modication of the invention useful as a high power amplier or oscillator at ultra high frequencies.

Similar characters of reference are used in all of the above gures to indicate corresponding parts.

Fig. 1 shows in cross-section one form of the invention. Hollow resonant cavities I and 2 are shown carried by the adjacent inner ends of conducting tu-bular members 3 and Il, the inner ends of tubular members 3 and 4 being closed by flexible corrugated disc walls 5 and 5. Walls 5.and 6 have centrally located openings through which drift tube 'I projects. The other fiat wall of resonator 2 is formed by disc 8, said disc having a centrally located aperture enclosing a grid structure 9. Drift tube 'I projects through ilexible wall 6 to act as a mount for grid structure I 0 positioned opposite and adjacent to grid 9. The form and operation of grid structures Q and IU and of resonator 2 has been disclosed in Fig. '7 of copending application Serial No. 343,528, filed July 2, 1940, in the names of William W. Hansen, Sigurd F. Varian, and Russell H. Varian, now Patent No, 2,311,658, granted February 23, 1943, and in prior disclosures. These grids may be omitted if desired. Resonator 2 is supplied with the two coaxial line leads II and I2, which are terminated in the resonator 2 by coupling loops I3 and I 4, respectively. Attached concentrically to tubular wall 4 as by means of a flange I5 is a tubular member I6, which may be of a metal lsuitable for sealing to a glass Iportion of the envelope (not shown) which acts as a support for cathode structure I1, as is shown in the aforementioned Patent No. 2,311,658 and in other dispassing very low frequency modulation voltages closures. On drift tube 'I is mounted disc-shaped grid structure I9. Wall 2|, which is electrically insulated from tubular member 3, supports grid in a cavity 22 opposite and adjacent to grid- IS, grid 20 and cavity 22thereby acting to suppress secondary electronsY or to prevent them from returning into resonator 7| Vand drift tube" l. Wall 2l is mounted as` an end plate in tu-Y bular member 23, which extends inwardly andV The' clearance space coaxially into resonator l. 24 between concentric tubular members 3 and 23 is adjusted in width tcobtain proper capacitive coupling between members 3 and 23, thus affording'aclosed path for the high frequency alternating currents which now'on the inner walls of resonator' i to vand from'grids I9 and 29',- while further providing insulation for any unidirectional or low frequency voltages whi'chmayY be appliedbetween grids I-S and '23. The space 24 may be Aoccupied by a dielectric material all", and may be made to have an extremely low impedance by means of a filter structure yet to be described. Mounted'in tubular Wall 3 are oppositely positioned coaxial linefmemfbers v25 and 26', which project through apertures 2-1 and 2i!Y in tubular wall 2,3, respectively, and which terminate Yin"- Sde resonator vi'ldlict'l V(jflllll'rlg loops 29 and 32, respectively. y*

In vorder to describe the concentric line vifllter systemus'ed with resonator I to prevent leak- -age ofV energy from resonator VI through space 2li, Figs. 2 and '3 are shown, illustrating a concentric line filter operating on 'the same `principle as thatjused with resonator I, as rwill be describedlbelow. AsA seen in Fig. 2, the outer tubular conducting member' 3I of thelter encloses concentrically a thin tubular dielectric member Slwhich nts closelyinto the inner diarneter of tube 3l.

Concentric with both tubes is a conductor '32, which, at approxi-mately quarter wave length intervals, expands intov approximately quarterl wave length :long Vconducting members which are substantially equal indiameter 'to' the inner diameter of Vdielectric tube 31.V The illustrated ilterV contains distributed inductance and vcapacity along its length. Sec-- tions Seare'effectively inductive While sections i5' are effectively capacitive, as diagrammatically illustrated 'in the' approximately equivalent cir- Y cuit oi Fig, 2. The relative distributed capacity and inductance Values vare determined vby the proportions selected for the relative dimensions y Elements 35;

electric material of tube 31. The unit is held rigidly` together by means ofinsul'ators 3S which t into opposite ends 'of tube'i3I and are heldin it by means'of screws 39.' The unit then per- Vforms as a `.series nductance multi-T-section uniform-section i'ilter.. Dielectric tubular meinber 3l 'may be omitted if desired, the relative di-` arneters of capacitive elements 35 and of outer conducting tubular members 3I being left ap:-

proximat'ely as shown. v

' Such a "filter 'may be used to"intro'duce volt= 4 ages such as heater voltages, cathode voltages, modulation voltages, etc., through a Wall of a shielding box surrounding a high frequency tube, or other high frequency apparatus, thereby preventing any high frequency radiation fromV leaking out of the box to disturb other high frequency circuits in the vicinity of the shielded tube, or' for other relatedV purposes; In Fig. 2 wehave shown the lter 'projecting through conducting wall 38 of such a shielding box. Screws 39 and the ends of conductor 32 serve as terminals for the -lter.

Normally very fev/,sections are needed in such a filterv to give substantiallyV complete attenuation ofthe' frequency that is (desired to be suppressed. The iilter circuit behind resonator I of lig..V l is shown with only two such sections,

operates, said lchambers lli? being 'about one quarv glass-to metal seal 4B.

ter wave length long. The inner conductor of the' concentric lineis made small in diameter as at 4E, and expands inf vdiameter to nearly equal 'the inner diameterv of tubular member 3 to form capacitativexelement 42, whose length is substantially a quarter wave length long. A-s previouslyV mentioned, spaces 2e and t8 may be occupied by a ribbonor tube of dielectric such a'sgthatfat 3l in Fig; 2 for supporting the inner iilter elements 'and resonator member 23 and, thus :removing somel of the vibration load from In this-event, capacitative element-42 will be electrically oneA quarter of a YWave length long "Where Wave length is measured in thei dielectric.V The inner conductor of the filter is then-'reduced in diameter at 41 to act as an inductive-element, lthe chamber 40, being. maderesonant to the frequency to be suppressed. Tubular conductor 41 is extended through end'V Wall- 44 of end chamber-Ml, said tube M extending through glass end bell 5, and thus; supporting the inner-conductor 4i of the iilter system Vand the inner Yportion 2|, 23 of resonator I, vand providing a lead -ior the unidirectionalor low frequency-modulating voltage to be impressed across gridsk I9 and 20.V Battery B is.- connected to provide a unidirectionalfvoltage across grids I9` and2, so that these grids are maintained atdiffering average or static potentials. As previously indicated, the above described filter arrangements provide for Yan extremely low impedance'at .the right endfof space 24. in Fig. l, looking -from right to leftin'Fig. l, thus increasing the ease of Vhigh.frequency current ow across the gap between the resonator sections and resulting. insubstantial .prevention of undesired leakage of high Vfrequencyv energy from resonator I. v

YIn explanation ofthe above, and looking from right toV left in Fig. 1, consider the unknownimpedanceV of the concentric line at the left endV of 'left quarter-wavesp-ace lll) to be ZX. Let'the characteristic impedances of the Vcoaxial transmission 'lines formed by' 'quarter-'Wave spaces 40 andV 42 be Zn andrZo' respectively. Thus yZt' is therefore very much smaller than Z0 under known concentric line theories. The line lirnpedance .at the leftv end of space 42 looking leftward is therefore 4quite high, being about and the line impedance at the right end of space pedance at the right end of space 24 looking leftward is very low, progressively lower than that at the right end of space 42, especially where space 24 is of the indicated quarter-wave dimension.

The above explanation is in accord with known theories of quarter-wave transformer theory.

The iilter elements 4l, 42, and 4I are made hollow and partition 5U is provided so that cooling water, introduced, for instance, in portion 5I and removed in portion 52, may be used to cool the end wall 2l of resonator I, especially providing cooling of the wall behind chamber 22 Where the spent electrons give up their energy.

The iianged ring members I6' and I5, fastened to resonators I and 2, respectively, and flange I8, clamped around drift tube 1, may -be used with tuning devices such as are disclosed in Patent No. 2,345,642, granted April 4, 1944. to Sigurd F. Varian and Russell H. Varian, and other disclosures therein mentioned.

To better understand the operation of the invention, the following theoretical analysis is given in connection with Figs. 4 and 5. Referring now to Fig. 4, there is shown diagrammatically elements of the structure shown in Fig. 1'; namely, a cathode emitter surface Il', and grids 9', I0', and I9', 2U', corresponding to grids 9, I0, and I9, 29 of resonators -I and 2, respecn tively. Let Vo be designated as the beam accelerating voltage, V1 as the peak value of the high frequency voltage between the buncher grids 9"- and I0', V2 as the corresponding voltage between the catcher grids i9' and 20', and V as a unidirectional voltage also applied between grids I9' and 29'. Also, let Io be the beam current before the beam enters grid 9'; and I, the electron current before entering grid I9'. The instantaneous voltage across grids 9', IU' is then V1 cos n t and across grids I9', 20 is V+V2 cos w t Where w is 21T times the operating frequency. Considering Fig. 5, let it be assumed that no electrons are to be actually turned back between the catcher grids; this requires that V2 be less than V-Vo. The resonator associated with the grids I9', 20 can then be considered as two resistances in parallel, R and RL, where R is due to losses in the resonators (the resonator shunt resistance) and RL is due to losses causes by loading, such as brought about in Fig. 1 by removal of energy from resonator I by means of coaxial line element 26. Let it be also assumed that the voltage V1 is such as to give optimum bunching of the beam; i. e., it is assumed thaty just stopped between the grids I9', 20. In that case:

V2=VoelV (1) RR V=1.16 IQRHL (2) If power is removed from the catcher resonator associated with grids I9', 20', such power is, by definition of RL:

E llt-2RL Combining (1) and (2) in (3):

P..=.58 10o/0+ tamil;

Then:

Eiiiciency (5) r 1 Pm :.58 RL P in 1 If it be assumed that V=O and if R is very large compared to R1., then Pout=.58 J0 V0 (6) Eiiiciency=-58 (7)v The Equations 6 and 7 are then applicable to al conventional high frequency tube of the type dis-4 closed above and in prior disclosures, and may be derived from equations in the two aforemen- Comparing Equations 6 and 9 it is noted that commonly greatly exceeds Vo, so that the power output of the present invention for a given Im is greatly increased over that of the conventional tube of this type.

The arrangement provided by the present invention has practical advantages which render it superior to a conventional tube merely having the beam acceleration voltage raised to Vo-l-V. As the electron beam traverses grids 9, I0 and I9, these grids intercept electrons which flow in a return circuit back to the positive side of the beam acceleration voltage source. The power loss represented by these return currents is obviously smaller whereV the acceleration voltage is Vo than where it is Vo-l-V. By introducing the additional acceleration voltage V at the catcher grids, the electron beam is subjected to thel same eiective acceleration at the catcher as would be the case if the original a-cceleration voltage was equal to Vo-l-V, and the power losses at the first three grids are held at a minimum.

Another practical advantage is that, where the beam acceleration voltage at the buncher is Vo, the electrons traverse vthe drift space between grids 9 and I9 more slowly and hence may become bunched during a shorter drift space length than would be the case where the beam acceleration voltage at the buncher was Vn-i-V. Thus, the invention enables the use of a shorter drift tube, providing a more compact tube.

Finally, since the power losses are low, it is possible to obtain a higher power output for a.A

shunt with resistances R and RL.

`constant It), V2 would be'- large. cause V2 tor be larger than Vo, thus reecting armonicoL given beanscurrentlu.. Byrthe. same token-iti isi possible.- toeoperate. tlie device; of they invention: at a higher power level than a conventicnal'tubev with increased beamacceleration at the buncher.

The previous discussion may be qualitatively verified by regarding the source of I in Fig. 5 as a constant current (given 'Iol generator in Then maximum power outputA occurs; when R=RL- In a conventional tube. of this type, the shunt resistance R is high, causing RL to be also high, so" that, with substantially constant current I (with This would Aelectrons back. .into the buncher resonator from. the 'region between "gridsY I9" and'2'lll The ad# :dition of VV prevents this occurrence.

Although the tube 'structure shown in Fig. 1 isadaptable for usefonlyfaslfa power-amplier or as 'anoscillatoig theoretical considerations mentioned in'. the aforementioned applications and .publications can be extended Vin describing modifications ci the present invention adaptable as-'detector tubes, as multiplier tubes, etc. One may replace resonator l of Fig. 1 with one of smallerV volume resonant. to a harmonicl of the launcher resonator* 2, as disclosed. in United StatesLetters Patent No..` 2,280,824, issued April 28, 19fi2, andin the laforementioned publications. For use as a multiplier tube, the dimensions of resonator l andA its attached lter structure will be determined .again byf-the output wavelength.

The modiication of theV present invention shown in Fig. 6 is Vparticularly useful as an ultra high frequency' power amplifier or as -an csaillator. Fig. 6 Villustrates a figure of revolution as generated by rotationv of the cross-section of Fig. l about an axis eccentric thereto, slightly modified` to wshow use of .afocusing. annular `cathode structure 53 and gridless annular resonators 54 and 55. From; cathode 53 a tubular, electron beam slightly focused by annular member 9i! passes through annular` buncher resonator 5ft' and. is thereby` velocity grouped or hunched in traversing Aannular drift tube 56, 's'. that it releases part of' its energy in annular' .resonator 5.5 being stopped; by wall 5T. Reson `nator 55' isV again made up of annular concentric,

portions.V One portion Aconsists of inner support-l V ing'cylindrical'conductingV member 58, 'apertured `rentsV flowing on the. inner surfaces of res-- onator 55,V meanwhile allowing a. unidirectionalv `voltage or a low frequency modulating voltage or both to be applied to the 4immediate'boundar-.

vies of the annular gridless orifices 61,58. Thus,..

it. will. be noted that. either-'oi the. parts-oi the resonator 55. associated withY ori-iices 6.1.. or. lili..` constitutean electrode.. y

Annuler lter sections d5, lil function. sims` ilarly. to4 the filter-described in Fig-1. Filter element i-. has .a .hollow annular internal. cav-f en-d Wall- 13 and are supported by two glass .-,belle j ar membersliiA and 14..- placed on-.a diameter ity 9 1-, which. may be supplied witnccolingwaten- Vthrough tubes l-l and 12V-which .extend througlfrY cylindrical, :chamherf'f between exible' di@ aphragms :6a and' fzrfbyffallowing; a cooling duid'r to iiow through axial bore'l in support 58 and out through bore 59'. A; further purpose of bores 59 and El is to. relieve pressures. in cham. berjj' caused `by differential Vdeformation'of the.' ilexibl'e diaphragms. 62, '63, 'and 82', 83.1'11 tuning resonators Y and' 54', respectively. Coaxial line coupling .elements .15' Y and 1.6 are provided 'in 'res-. onator llgjandV coaxial line coupling'elements 11' and '18'are mounted in `resonator't in the man--V ner shown inFig.' 1. VFlanges 19., 80 and 8| are provided "for 'any conventional resonator 'tuning devices as. described in the aforementioned applicationsand in others therein referred to. The. pipes Tl and i2 serve to support the inner por-. tion of annular resonator '55 'and its associated.; an'nul'ar'lilter` element, supplycooling Vmeans to said 'resonator portion, and provide meansfor' impressing 'the voltage V across the two sections 61,168' of resonator 55;* Y

From 'the above description of Figs. l and' 6. it is. evident 'to onev skilled in' the art that 'a' similar resonator and filter Vunit construction` may be applied to the buncher resonator of any high frequency tube of the present type, thusi providin'g'the possibility of introducing` a undirectional voltage or a'low frequency modulation voltage to the .gridsfof ltheIbunlbl'ier resonator. It.. is alsoevident to one skilled vin the art, that a high power output structuremay be 'obtained' in. amanner similar to that inwhich the structure' o'i Fig.. 6 was conceived by placing the axis about. which the cross-section of Fig.- l.v is rotated perpendi'cular. tothe axis cffFig. 1, instead of parallelfto .the axis of Fig. 1. as was done in ob-Y taining the structure .of Fig. 6.

YAsmany changes could be made-in the above construction and. many apparently widely different embodiments of this invention could beV made. Without departing from the scope thereof, it. isintended thatv all matter contained in the above vdescription or shown-in the accompanying drawings shallbe interpreted as'illustrative and not ina limiting sense.

What is claimed is:

1. HighV frequency apparatus-comprising means includinga cathode for projecting an electron.r stream alongfa predetermined path, apair ofY cavity resonatorsfspaced from said` cathode and each having a pairy ofv axially aligned apertures` along said path and similar grid structures-Y mounted respectively inV each of saidy apertures',V whereby the resonator closerl toA said cathode isY adapted. to velocity' modulate the `electronspass; ing; throughV its pair of grid structures and the` resonator farther Vlronrsaidicathode is adapted.. tio vextract; energy from the V'electrons passingy through'its pair of' grid' structures, and poten'-v tial sour-ci-zv-means. coupled to the grids of 'one oi? 'said' resonatorsfo-r maintaining said latter" grids 'atA different average p'ote'ntials, whereby for a given beam current greater power output may be obtained from said apparatus'.-

21 HighY frequency apparatus comprising means: including" a cathode for producing a stream of' electrons flowing along` predetermined path, a firstA cavity resonator spaced from 'said cathode` and' surrounding said path and coupled to said stream tovelocity' modulate the electrons thereo'fja drift tube' defining'A aI eld-free space sur'- rounding said path` beyond. said resonator, a second cavity resonator' surrounding the path of said stream beyond. vsaid drift tube and coupled of. wall 1.3. Heatmayalsqgbe removediromr'the' to said stream toA extract high frequency energy therefrom, said second resonator comprising two relatively insulated sections and potential source means coupled to said sections for maintaining said sections at different average potentials.

3. Apparatus as claim 2 wherein each of said sections is constituted in part of an apertured wall, said walls being insulate-d and in the path of said stream, said potential means including a source of unidirectional potential, and means connecting said source between said walls with the ypositive terminal connected to the wall farthest from said first cavity resonator, whereby increased power output may be obtained from said apparatus at higher efficiency.

4. High frequency electron velocity modulation apparatus comprising a pair of spaced aligned hollow resonators each having a pair of electrompermeable wall regions, means defining a field-free drift space between said resonators, and -means in said apparatus including a cathode outside said resonators for producing an electron stream and for projecting said stream successively through the regions of one of said resonators, said drift space and the regions of the other resonators, stream may ybe velocity modulated during its traverse of the gap between the electron-permeable wall regions of said one resonator and said other resonator is adapted to extract energy from said stream during its traverse of the gap between the wall regions of said other resonator, at least one of said resonators being composed of two insulated capacitively coupled conductive sections.

5. Apparatus as in claim a, further including a source of unidirectional potential and means connecting said source between said sections whereby increased power output at higher efficiency may -be obtained from said apparatus.

6. High frequency electron discharge apparatus comprising means including a cathode for projecting an electron stream along a predetermined path, means spaced along said path from said cathode for velocity-modulating the electrons of said stream, means dening a held-free drift space surrounding said path beyond said modulating means, a cavity resonator beyond said drift space having an electron-permeable wall region in the path of said stream, whereby said stream is directed into said resonator and said resonator is adapted to extract energy from said stream, said resonator comprising a pair of insulated conductive sections, and means coupled to said sections for impressing a direct voltage therebetween for maintaining said sections at diiferent average potentials whereby increased power voutput and higher efficiency may be obtained from said apparatus.

7. Ultra high frequency apparatus comprising means including a cathode for projecting an electron stream along a predetermined path, means along said path spaced from said cathode for velocity-modulating the electrons of said stream by a high frequency signal, means defining a eld-free drift space surrounding said path .beyondsaid modulating means, whereby said velocity-modulated electrons may become density modulated by velocity groupingA action, and means in the path of said density modulated electrons for extracting high frequency energy therefrom, said last-named means comprising a pair of relatively insulated electronpermeable members in the path of said stream, means coupled to said members and defining a hollow cavity resonator, a source of electron-acwhere-by said electron .i

celeratng voltage, and means connecting said source between said members, whereby increased power may be extracted from said stream at higher efliciency.

8. Ultra high frequency apparatus comprising means defining a hollow resonator including two concentric'closely spaced insulated members, the inner of said members being substantially a quarter-wave length long at the operating frequency thereof to provide a quarter-wave transmission line section of low characteristic impedance with the outer of said members, and filter means within said apparatus blocking leakage of high frequency energy outwardly from said resonator through the gap between said members, said lter means comprising a concentric transmission line having inner and outer conductors connected respectively to said respective resonator members, said transmission line having a section of a length substantially equal to a quarter-wave length, and of a characteristic impedance substantially larger than the characteristic impedance of said rst-named quarter-wave length section, whereby a very low impedance is obtained at the gap between said two members. v

9. High frequency apparatus comprising a cylindrical outer member, a second member concentrically mounted within said outer member and projecting therewithin and connected to one end of said outer member, a third wall member within said outer member opposite the inner end of said second member and insulated from said outer and second members, said three members defining a hollow cavity resonator, and means preventing leakage of high frequency energy from said resonator .by Way of the gap between said 'outer member and said wall member, said lastnamed means comprising conductive means within said outer member forming a coaxial transmission line therewith and having successive portions of length substantially equal to a quarter-wavelength at the operating frequency of said resonator and of alternately relatively large and small characteristic impedance whereby the impedance at said gap is transformed to a low value to prevent said energy leakage.

10. High frequency apparatus comprising a cylindrical outer member, conductive means deiining a resonator wall connected at one end of said outer mem-ber, further conductive means defining another wall of said resonator insulated from said outer member and mounted therewithin, said outer member, conductive means and further conductive means deiining a cavity resonator, and means preventing leakage of high frequency energy out of said resonator by way of the gap between said outer member and said insulated member, said last-named -means comprising conductive means within said outer meinber forming a coaxial transmission line therewith and having successive portions of length substantially equal to a quarter-wavelength at the operating frequency of said resonator, the rst of said portions having relatively large diameter forming a concentric transmission line of relatively small characteristic impedance with said outer member and the second of said portions having relatively small diameter to form a relatively larger characteristic impedance with said outer member, whereby the impedance at said gap is transformed to a low value to prevent said energy leakage. s

il. High frequency apparatus comprising a tu'- bular conductive member, conductive means de- 'accanto Af-acavity resonator, .and means preventing Vleakage fof high frequency energy out of said reso- "natorV by Way of` the gap 'between said tubular member and said insulated .wall-.defining means, fsaid leakage-preventing means comprising a concentric transmission line having inner and outer conductors connected to said 'tubular memliber' and saidfwall-dening means, said line hav'- fing a section of relatively low characteristic irnpedance and of a length of substantially onequarter Waveflength at the operating frequency of said resonator and adjacent said resonator', and alsohaving a second section connected to `ysaid first lsection land of relatively high characteristic impedance comparedto thatof said first section and of a length of substantially one- .quarterv/ave-length,

12. High frequency apparatus comprising fmeans defining a hollowresonatorA including a pair of closely spaced concentric tubular members having a tubular dielectric member therebetween, yan endjwall connected to oneoi lsaid ,members a v:flexible wall connected to the other of said. members, .and a reentrant hollow tubular member .mounted onsaid flexible Wall concern ,trically with respect to 'said tubular Vmembers 4and having a flat end face substantially lparallel tosaid.firsuend wall and adjacent thereto.

`13.Apparatus as inclaim `12, fui-.ther'including means` for .-projectingfan electron stream ax- V ially .projected .from externally vof said resonator and means. coupled .to said .sections .for maintaining vsaid sections at .different average-potentials.

.15...Apparatus .asin claim.14, Wherem. said re.- entrantport-ion vis .axially adjustable with respect to'saidA sections, whereby tuning of said reso- .nator may be effected.

16. A high frequencyelectron discharge -device comprising acylindriCal outer memberfhaving a concentric. .axially reentrant portion, said reen- .trant .portion having a concentric openingtherein, a.second cylindrical'member positioned con.-

`centr-ically.` within said 4.firstmenuber.. and insulat-V jed therefrom, Y.and formingA a` hollow. resonator withsaid. nrst. member by capacitive. coupling therewithgone of ,said .members having an .lectron permeable region through .whichan .electron .beam may .be projected, and ltermeans V.also positioned within. saidfirst .member for preventing high frequency energy leakage from said resonator through the .insulation between said first andsecondmembers. Y Y

17. A device as in claim 16,. in Which said `lter vi12 Y device f comprises" la plnralityrofi sectionsf o coifductor forming vquartezt-Wave'transmission'dine .sections swith said y'outer V'niemberg said ysections beingy spaced' by: `quarter-Wave capacitive loading sections.

18. A high frequencyelectronrvelocity modulation device comprising means zd'ening ahollow resonatorV having 'tivo generally iannulan; capacitatively coupled, concentric; conductive members, one ofxsaid memioershaving asubstantially armularY felectronspermeable v:region through which an lelectron beam `may. be; projected from the exterior of said'resonator., and means coupled to said members'forzmaintaining said members at differing .average potentials,

filter means Within said Vdevice for .blocking leakage `of high Vfrequency'energyfrcmi vsahreso' hater, said filter means comprising a concentric conductor transmission line having .inner and `outer conductors". 'connected to vthe respective resonator members, with said resonator.. members -forming a Vquarter-w'vave capacitative loading section in said line.

19. 'High frequency lapparatus vcomprising :means including acathode :for producing ran electron stream, ar pair of cavity resonators vmounted along the Apath of said 4stream"spaced from said cathode and :separated ,by a. held-'free `drift lspace surrounding vsaid streampath, each `of said resonators :having'a'y pair of electron-pe meable wall portions serving-as electrodes inthe path of saidstream, whereby-,the pairof; said electrodes closer to said .cathode vis. .adapted'to velocity modulate said electron stream andthe .other-:pair of said electrodes is adajgited'` to eX- ;tract @energy from saidstream :one of.. said -res- .zcnators having'tvvorelatively insulated sections, and a 'source' of modulating-.voltageconnected be tween :said sections.

20. .High 'ifrequency'fapparatus as in claim 19, further including means :couplingsaid. resonators together, whereby self-sustainedoscillations modulated .by said Avoltage vare produced.

21. .An electron dis-charge devicecomprisingan :outer cylinder havingY affixed end wall at vone Yend thereof and-,a flexible .end vWall ,atthe .other iend thereof and having a tubular Ypassage. coaxial'vwith the cylinderthroughibothend `walls and .spaced bothI .from thev axis .and from the V'cylindrical Wall, an annular `cathode opposite one `end lof said tubular passage, and an rannular ,electrode at ,the-other 4end of. said passage.

22. An electron discharge device. vcomprising .-an outercylinder having. affixed end l. wall at one endthereof and a` exible. .end Wall atthe other 4 end thereof andhaving a. tubularpassage coaxial With-the cylinder through both endwalls and spaced both from theY axis .and .fromthe .cylin- .drical wall, andan .annular cathode` opposite one end .of said .tubular passage.

WILLIAM W. HANSEN.

r REFERENCES. VGITED. :The following referencesare. vof record .the

- (Other referencesY olifllwingpage) Number 13 UNITED STATES PATENTS Name Date Llewellyn Feb. 20, 1940 Hahn Nov. 5, 1940 Trevor Nov. 12, 1940 5 Zottu et al Jan. 14, 1941 Linder Feb. 25, 1941 Trevor Apr. 29, 1941 Varian May 20, 1941 Maslov Aug. 19, 1941 10 Bruche et a1 Oct. 7, 1941 Hansen et a1 Oct. 21, 1941 Morton Mar. 31, 1942 Number Number Name Date Samuel May 5, 1942 Varian et a1 June 30, 1942 Litton Dec- 8, 1942 Ryan July 6, 1943 Zalesak Sept. 21, 1943 Clord May 21, 1946 FOREIGN PATENTS Country Date Australia. Nov. 4, 1937 Germany Sept. 29, 1938 France May 20, 1935 

